Arginine vasopressin (AVP), a posterior pituitary peptide hormone, has been shown to have several non-renal actions including the maintenance of learned avoidance behaviors, and recently, in humans, improvement in cognitive functioning. Preliminary research in our laboratory has confirmed some of these behavioral effects in animals and begun an attempt to examine the behavioral and physiological basis of this effect. The present proposal for research will focus on determining the physiological mechanism by which AVP produces its behavioral effects. Behavioral experiments will concentrate on examining the effects of AVP in rats on two tests of "memory", an active avoidance task and a spatial forgetting test, and one test of "emotionality" the Geller-Seifter conflict test. These tests have been chosen to control for the nature of the unconditioned stimulus (aversive vs. appetitive), motor debilitating effects, and motivational effects of AVP itself. The importance of peripheral mechanisms related to the classical endocrinological effects of AVP will be determined by using these behavioral tests and analogs of AVP, some of which are specific antagonists of certain endocrinological effects. In addition, an attempt will be made to identify the distribution and site of action of exogenously applied AVP using radioimmunoassay and intracerebral injections. This basic research directed at understanding the mechanism of action of the effects of vasopressin on behavior has important implications for the possible therapeutic use of vasopressin in cognitive disorders associated with aging, and other biologically based learning disorders.